The interactions among the prefrontal cortex, hippocampus and dopaminergic systems are thought to play a role in schizophrenia. However, the nature of such interactions from a physiological perspective are not yet fully understood. Establishing how a hippocampal deficit impacts on physiological measures of prefrontal neuron activity and how dopamine modulates these interactions may provide a significant contribution towards establishing a comprehensive animal model of this devastating disorder. In this proposal, plans are presented to assess the impact of a number of manipulations in the hippocampal afferents to prefrontal cortical neurons intracellularly recorded in vivo: 1) determining the input responsible for the transitions to the active periods in prefrontal cortical neurons exhibiting a slow oscillation in their membrane potential and cell firing; 2) establishing the role of hippocampal afferents on such oscillations and their source input by assessing the effects of hippocampal stimulation and by performing similar experiments in animals with a hippocampal lesion; 3) assessing the effects of a neonatal hippocampal lesion on these interactions in adult animals as an initial attempt of testing the hypothesis of a developmental hippocampal disturbance resulting in hypofrontality; 4) testing the effects of rearing animals in social isolation on these interactions, with the aim to determine the actions of an environmentally-induced brain deficit that in many respects exhibits alterations resembling schizophrenia; and, 5) determining the glutamate receptor subtype involved in hippocampal-prefrontal interactions by studying the actions of glutamate receptor agonists and antagonists on synaptic responses in prefrontal cortical cells recorded in vivo.